The cover was addressed to Courbevoie on the Seine.
Courbevoie is a suburban area about 10 km northwest of central Paris.

The cover requested routing Via America.

The cover would have been sent from Yokohama to either Seattle or San
Francisco by boat.
It would then be sent to New York City by rail and then on to France by
boat.

Unhappily, we don't know whether there are any transit marks on the
reverse.
There should be indications of arrival in a United States port and
transit/departure from New York.
I would also expect a Paris receiver of some sort.